Last weekend was the OTHG MX LACR South National. Racers from all over California and surrounding areas came out to battle it out for two days of racing. All the racers rode at least 2 motos per day and a lowest overall score for the weekend would decide the overall winners. With summer coming to an end there were cooler temps in the morning and evenings. Arriving the Friday to a fully packed track with many racers camping out. The LACR track crew did a great job to prepare the track. The course is about 1.5 miles long and nets around 2 minute lap times.
The N2Dirt riders showed excellent speed. With onsite suspension support the riders were able to get bikes checked out on dialed in before the races. The track got rough super fast with a lot of racers trying to set the pace to win. Our crew was busy setting sag and consulting riders on line selections and racing strategy.
We were able to connect with the LITPro team to analyze on track data to improve lap times. Litpro is high definition GPS over-laid on an over head photo of the most current track design. The data is very helpful to understand where you can make up time on the track. The guys were able to explain the applications power in racing. Adding sensors to test suspension speed and travel is the next step in the game for us. Real time data of what the suspension is doing to aid in tuning. This will help eliminate some of the guess work of getting good settings. Along with these options the Litpro shows what sort of G forces the rider is experiencing. There is a direct correlation of G force and lap times. We look forward to working with Litpro in the future.
Several N2dirt riders won throughout the weekend. Here’s a list of the winners:
With the new bikes hitting the showroom floor we have had a full year to put the new KTM WP XPLR suspension through it’s paces. As the budget for suspension tightened up it is clear that we will see some shortcomings from the performance and modifications will be necessary for the serious rider or racer. Some issues to address will be the effectiveness of the fork compression adjustment and the long term durability of the shock.
WP XPLOR 48 Fork
With the 4CS a thing of the past we are on to a redesigned open chamber fork. Keeping with the single adjuster theme WP adjusts the XPLOR on the top with rebound and compression adjuster. Some models come with external pre-load adjusters. We have found the compression adjuster to make very little difference through out the range and the fork lacks sufficient dampening control for any aggressive riding. With most of the damping control isolated to the rebound side the compression side has a plunger style adjuster. This plunger valve body has an adjustable port area and an open cartridge via 4 holes just below the cartridge rod bushing. The plunger can never be totally closed off or else the fork would hydraulically lock out. This is a simple and not very effective design. The more parts they can leave out the lower the budget can be. Essentially just to get the bike off the showroom floor.
Total cartridge replacement. With high quality fork tubes replacing the lacking internals is a viable option. MX-TECH has designed and tuned a really nice complete cartridge fork that comes with necessary springs. LINK
Dal Soggio Sphere is another cartridge kit to replace the internals with high quality parts. Springs are additional. Some modifications are necessary for installation and it is recommended to have a professional install them.
DS also supplies an upgraded kit to add the missing parts called the XP-ONE.
Focused Fork revalveis available but added parts are recommended to gain added compression adjust-ability. Base valves and a 2nd mid-valve.
WP XPLOR SHOCK
WP goes for a lighter and less expensive design for the shock. Down to 46mm this shock is prone to overheating and fading with less shock fluid to control damping. The shock has a similar feel to the PDS as it has a tendency to have a fast rebound and kick up in consecutive bumps. The best solution for the shock is to revalve to correct the high speed damping for square edge bumps. Increased capacity by adding a TANK from MX-TECH. This will help keep the shock cool by lowering friction and adds overall oil capacity. The tank replaces the OEM plastic piston with a coated aluminium unit.
The second piston design has been simplified. Instead of the bottoming needle there is now a Ohlins or MX-TECH style piston and cylinder to aid in damping for the last part of the stroke. Along with the new piston there is a check valve.
If you have any questions or need to set up an appointment feel free to call us 661 252-0269.
These improvements include improved handling, wheel travel, and bottoming control.
The image below has wheel rate graphs vs stock positions to illustrate how our linkage can accomplish this by changing the rear suspension movement. The addition of this linkage is the first modification before any spring change or shim setting as they will need to be matched.
Last weekend at the REM races, N2-Dirt’s Brian Bolding found five KTM 350SXF’s with loose crank nuts on the clutch side. This nut cannot fall off the end of the crank, but it can spin against the case, wear enough aluminum away to clog the oil lines and even allows the snap ring and crank seal to walk out. We recommend that you check the nut on the end of the your KTM 250 or 350 crank — it does require draining the water and removing the impeller to get to. The first signs are some strange engine noises, followed by the cam chain tensioner’s hydraulic lines getting clogged and eventually a ton of aluminum in your oil filter (you may have to cut the oil filter open to see it). We talked to KTM and expect a KTM dealer bulletin to be sent out. This only affects KTM 250SXF and 350SXF engines and not the 450SXF.
The 17.5 AER Fork received an update to the Air piston. We have found these to feel better with less friction after they are torn down and greased. The OEM grease is not sufficient and is grabby in the beginning of the range. We are updating all the older forks with this piston and the better grease. This is a great fork and a good design but needs some attention. Send us your fork and we can get you updated with the new piston and re-valve at the same time.
First impression is huge improvement of bottoming resistance over revalved shock. I used to have a good amount of rub marks on the fender after a long moto and now I am just noticing the dirt is just getting rubbed off and no tire mark. The presents of the bottoming system is there and you can feel it but as long as your compression clicker isn’t backed out to far you don’t feel it come on too much when it’s low in the stroke.
Watching the action of the rear end of the bike looks so much different than a stock setup bike. Much more controlled motion and planted feel. Traction is greatly improved as you don’t need a really stiff low speed compression stack to compensate for bottoming resistance.
With the triple adjuster you can really dial in the low speed rebound to keep the back tire biting when unloaded on entry of a low speed roller into a turn.
Seat bounce any jump face out of a turn with confidence that you won’t blow through the entire stroke instantly.
The balance of the bike has improved to match the bottoming resistance of the AER Fork. While we are happy with the results so far we aren’t done tuning yet and will continue with races as weather is permiting. Stay tuned!
2017 KTM and Husky models fitted with the AER Fork contain a solid clamp mid valve or a wave washer mid valve. Along with having tuning constraints they are prone to failure and WP updated the new models to a sintered piston. We have a fix the Aer leaf spring with mid valve piston will also give the fork a much better feel. It is highly tuneable and durable.